Take the elevation of tabbed browsing to the core of the user experience. While Firefox and Microsoft Internet Explorer 7 both support simultaneous tabbed navigation, Google Chrome is built on it. Tabs have been elevated to the top of the interface, and Google has introduced separate processes for each tab, so one tab’s glitch doesn’t crash the whole browser — as is the case with IE 7 and Firefox. Here’s a screen grab from the comic book, created by the great Scott McCloud, that Google used to unveil Chrome:

Clearly Google believes the future of the Web lies in toggling — between static pages and rich applications, between entertainment content and productive tasks. If it proves to be correct, and consumers increasingly channel their attention through numerous tabs residing shoulder to shoulder in the narrow confines of a browser, marketers will be forced to reconsider how they deliver — and measure the impact of — their display ads.

Among the questions such a presumed future raises: What is the impact of simultaneous browsing on metrics like page exposure time and ad exposure time? How does it affect the overall number of ads served to any given Web user, as well as the effectiveness of those ads?

Also, what are the best ad placements to leverage a tab-addicted society? For instance, some publishers claim users of IE7 and Firefox have exhibited higher click-through rates on horizontal banner ads at the top of Web pages. But the evidence is anecdotal. Very little research exists on the effect of tabbed or simultaneous browsing on digital ads.

That may change. JupiterResearch hasn’t yet looked into the phenomenon, according analyst Emily Riley. However she indicated it hopes to do so in the future.

Until that happens, advertisers can only guess at the impact of tabbed browsing on their ads.